The present invention relates to a centrifugal clutch, and more particularly to a clutch incorporated into a power transmission system for transmitting a driving force generated by a power generator such as an internal combustion engine to a working tool in a working machine such as a grass trimmer.
In a centrifugal clutch, a clutch boss on which clutch shoes are provided is used as a drive member fixed to an output shaft of a power generator such as an internal combustion engine, and a clutch drum shaft of a clutch drum is used as a driven member positioned in coaxial alignment with the clutch boss. Under this condition, a driven side fixture for rotatably supporting the clutch drum shaft is fixed to a drive side fixture such as an engine body. During the operation of the clutch shoes of the clutch boss, the centrifugal force causes the clutch drum to uniformly firctionally engaged with the clutch shoes on its inner circumferential surface, to thereby smoothly transmit driving force from the clutch boss side to the clutch drum side and suppress the generation of vibration as much as possible. Conventionally, the coaxial alignment of the clutch drum shaft relative to the clutch boss has been performed by providing positioning means such as knock pins to the drive side fixture and the driven side fixture and aligning the positioning means with each other for coupling the driven side fixture to the drive side fixture. However, in such a conventional coaxial alignment, it is necessary to provide the positioning means such as knock pins to both the fixtures. In addition, the positioning means per se must be arranged with high precision. This is troublesome and time-consuming in manufacture and would lead to an increased cost.